8 10 3

3

7

8 x 10

6

6

5

Under-predicted

4

4

3

Under-predicted

2

2

Over-predicted

Over-predicted

1

0

5 10 3

10 x 103

0

1

2

3

4

0

2

4

6

8

Predicted

Predicted

The term (ρ0wa) is in kilograms per meter. It is

resistance of a trailing wheel can be considered a

interesting to note that adding a term for the fourth

constant in most cases; however, snow falling back

axle adds little to the accuracy of the equation and

into the rut behind a leading wheel results in

forces the coefficient for the third axle to be nega-

higher values and seems to be related to initial

tive, a physical impossibility. The rationale for the

snow depth. The true effect of wheel width on

ratio of snow depth to the depth of 0.22 m is to

resistance of a leading wheel is still not known and

should be studied using a numerical technique

account for the effect of snow falling back into a rut

where other parameters can be held constant. Lim-

behind a leading wheel in deep snow. The trailing

ited data were presented for undercarriage drag,

tire coefficients obtained are higher than antici-

and since this will be the primary cause of immo-

pated, and this is thought to be attributable to

higher loads on the trailing axles for most of the

bilization on level surfaces, it deserves further

vehicles in the data base, as compared to the CIV,

investigation.

which has less weight on the trailing axle.

A new and significantly improved algorithm

Other forms of the term (ρ0wa) were investi-

for predicting sinkage and motion resistance in

gated using the ideas presented earlier; little or no

undisturbed snow was presented. This improved

improvement was found in the regression analy-

algorithm should be implemented in current cold

sis. Figure 15 shows a comparison of the predicted

regions mobility models.

vs. measured resistance. It can clearly be seen that

eq 8 produces excellent results and a marked im-

provement over earlier algorithms. Table C1 con-

tains the actual predictions and residuals.

vehicle: Hardware and software. USA Cold Re-

gions Research and Engineering Laboratory, Spe-

cial Report 83-3.

Several aspects of the interaction between snow

and a wheeled vehicle were investigated. The

tance in shallow snow. *Proceedings of the 9 Inter-*

17

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